Curtains of the hinged slat type are customarily mounted to move in accordian fashion between an opened position with the curtain material compressed at the sides, to a closed position with the curtain material spread out across the window opening and the inner curtain edges abutting at the mid-point of the rod. It is desirable, however, to provide a light-tight abuttment when the curtain is in the closed position, and to do so requires an extra slat in one curtain half to provide an effective overlap at center line of the window. The extra slat, however, creates a further problem. If the curtains are supported on a traverse rod, in the conventional manner, one of two things happens. Either the curtains cannot be fully closed at the mid-point of the rod, or they cannot be fully opened to the sides. This is due to the extra slat on one side. Thus, if the cords are adjusted so that the curtain opens fully to the sides, drawing the curtains to the closed position requires pulling one side of the curtain to a point beyond the mid-point of the rod. When this happens, the effect is particularly disturbing because the eye immediately sees the difference in the spacing of the slats on one side of the curtain than on the other. Also, the center line of the curtain is not exactly in the middle and the human eye readily notices such an imbalance. Conversely, if the pull cords are adjusted to make the curtain halves meet perfectly at the mid-point of the rod and with the slats all perfectly spaced, then when the curtain halves are pulled to the opened position, one side reaches the fully gathered position before the other. This leaves the latter side in an ungathered position which is likewise unsightly and is readily noticed by the human eye.
Accordingly, an object of the present invention is to provide a lost-motion means for fully opening a pair of curtain components in which one component has substantially more material than the other, and to fully close the same components with a light-tight overlap, at the center line of the curtain. A further object is to provide a means for externally adjusting master carriers adapted to accomplish the foregoing objective for various rod lengths. Still a further object is to provide such a means for use with hinged slat type, "woven wood" curtains.